Adding Kalk to Vinegar dosing

[TheKyle]

My 250gallon system runs nutrient heavy, such that I dose a lot of vinegar for nutrient reduction (just under 220ml/day currently). For some time now I have been adding Kalk directly to my 5% vinegar in order to combat the ph lowering effect of dosing acetic acid. I currently mix 1 cup of Kalk with a full 1.32 gallon vinegar bottle. At this rate the Kalk fully dissolves and the ph of the solution is presumably higher that my api test can detect (ph>=8.8). I’ve been thinking about my dosing regiment recently have been wrestling with a few questions below. I appreciate any input.

1. Will my solution of Kalk and vinegar ultimately have a ph raising or lowering affect? I would assume ph raising effect due to the Kalk saturation. Is this correct?

2. Currently I only dose this solution in the day, spread out hourly. The idea being to avoid oxygen from being depleted at night due to vinegar consuming bacteria. Assuming I am correct about the solution raising the ph of the aquarium, should I also be dosing as night? I run a reverse lighting schedule refugium. Does the concern of lowering oxygen levels at night out weigh the concern of ph swing at night? To sum it up; would it be better to dose over 24hrs, just during the day, just at night?

3. Out of curiosity. Does anyone know what is the max amount of Kalk that can dissolved in 5% vinegar? I guess I could experimentally find this by adding more Kalk until it won’t dissolve anymore. I’m really wondering if the ratio of vinegar to Kalk I use is good, or if I should try adjusting it. Any reasons I might want to change the ratio I am using?

Thanks

 

[Randy Holmes-Farley]

When you say ultimately, that’s a complex question that cannot be answered in general. I suspect that so much vinegar relative to limewater will cause pH lowering, and some of that pH lowering only happens when the acetate is metabolized to CO2.

I will note that premixing them, while not my preferred method (I like adding them Independently to control the timing of each) will not alter the pH effect relative to adding them close in time but separately.

 

[TheKyle]

When you say ultimately, that’s a complex question that cannot be answered in general. I suspect that so much vinegar relative to limewater will cause pH lowering, and some of that pH lowering only happens when the acetate is metabolized to CO2.

I will note that premixing them, while not my preferred method (I like adding them Independently to control the timing of each) will not alter the pH effect relative to adding them close in time but separately.

Interesting. Thanks for the explanation. That makes complete sense.

You mentioned separating lime water and vinegar to control timing. So if I were to add lime water and vinegar separately what would be a preferable timing? Lime water 24 hrs and vinegar during the day? Or maybe, lime water at night and vinegar during the day?[/QUOTE]

 

[Randy Holmes-Farley]

I want to deliver vinegar in the mid morning to mid afternoon when O2 is highest (metabolism of it consumes O2) and pH is highest. I usually added limewater by ato 24/7, but other timing schemes also make sense (night to offset pH drops, day to offset alk drops)

 

[TheKyle]

I want to deliver vinegar in the mid morning to mid afternoon when O2 is highest (metabolism of it consumes O2) and pH is highest. I usually added limewater by ato 24/7, but other timing schemes also make sense (night to offset pH drops, day to offset alk drops)

Good stuff to know here. Thanks for sharing your approach.